1. Field of the Invention
The present invention relates to a wireless communication system, and more particularly to a method and apparatus for transmitting and receiving system information in a wireless communication system.
2. Discussion of the Related Art
A brief description will be given below of a super frame header (SFH).
A base station (BS) transmits system information to mobile stations (MSs) through an SFH. The SFH is located in a first subframe contained in one superframe. The SFH is divided into a primary SFH (P-SFH) and a secondary SFH (S-SFH).
Table 1 shows a P-SFH Information Element (IE).
TABLE 1SyntaxSize (bit)NotesP-SFH IE format ( ) { LSB of superframe number4Part of superframe number S-SFH change count4Indicates the value of S-SFH change count associatedwith the S-SFH SPx IE(s) transmitted in this S-SFH change cycle S-SFH size extension20b00: SizeSPx,extension = 00b01: SizeSPx,extension = 80b10: SizeSPx,extension = 160b11: SizeSPx,extension = 24 Number of repetitions for S-SFH2Indicate the number of repetitions used for S-SFH (NRep,S-SFH)transmission.0b00: reserved0b01: 60b10: 30b11: 1 S-SFH scheduling information2Indicates which S-SFH SP IE is included in S-SFHat this superframe0b00: S-SFH SP1 IE0b01: S-SFH SP2 IE0b10: S-SFH SP3 IE0b11: no S-SFH S-SFH SP change bitmap3Indicates the change in the content of S-SFH SPxIE(s) between current SFH and previous SFH associatedwith the S-SFH change count.If bit#0 (LSB) = 1, change in S-SFH SP1 IE. Otherwiseno change in SP1 IE.If bit#1 = 1, change in S-SFH SP2 IE. Otherwise nochange in SP2 IE.If bit#2 (MSB) = 1, change in S-SFH SP3 IE. Otherwiseno change in SP3 IE. S-SFH application hold indicator1Indicate the S-SFH change count value used todetermine the S-SFH SPx IE content to apply in thissuperframe:0b0: Use S-SFH SPx IE content associated with thecurrent S-SFH change count0b1: Use S-SFH SPx IE content associated with (thecurrent S-SFH change count − 1) modulo 16 Reserved3The reserved bits are for future extension.
The P-SFH IE is transmitted at every superframe, and includes 4-bit Least Significant Bit (LSB) information of the SFN and information associated with the S-SFH IE. The S-SFH IE—associated information includes an S-SFH change count that indicates version information of a currently transmitted S-SFH; S-SFH scheduling information that indicates which secondary super frame header subpacket information element (S-SFH SP IE) is included in the corresponding superframe; S-SFH size that indicates the number of LRUs allocated for S-SFH transmission; S-SFH number of repetition that indicates a transmission format of the S-SFH; and S-SFH SP change bitmap that indicates which S-SFH SP IE is changed. The size of the S-SFH SP change bitmap field is identical to a total number of S-SFH SP IEs.
Table 2 shows the S-SFH IE format. The S-SFH transmits actual system information. The system parameter and system configuration information transmitted through the S-SFH are classified into S-SFH SP1 IE, S-SFH SP2 IE, and S-SFH SP3 IE. S-SFH SP1 IE includes network reentry information. S-SFH SP2 IE includes initial network entry and network discovery information. S-SFH SP3 IE includes the remaining requisite system information for network entry or network reentry.
TABLE 2SyntaxSize (bit)NotesS-SFH IE format ( ) { if (S-SFH Scheduling information == 0b00) {  S-SFH SP1 IE ( )SizeSP1Includes S-SFH SP1 IE in Table 832.The size of S-SFH SP1 IE depends onFFT size.For 2048 FFT,SizeSP1, default = 96For 1024 FFT,SizeSP1, default = 90For 512 FFT,SizeSP1, default = 84 } else if (S-SFH Scheduling information == 0b01) {  S-SFH SP2 IE ( )SizeSP2Includes S-SFH SP2 IE in Table 833.The size of S-SFH SP2 IE depends onFFT size.For 2048 FFT,SizeSP2, default = 96For 1024 FFT,SizeSP2, default = 90For 512 FFT,SizeSP2, default = 86 } else if (S-SFH Scheduling information == 0b10) {  S-SFH SP3 IE ( )SizeSP3Includes S-SFH SP3 IE in Table 834.SizeSP3, default = 77 }}
S-SFH SP1 IE, S-SFH SP2 IE and S-SFH SP3 IE having different periodicities are transmitted at different times. Table 3 shows transmission periods of S-SFH SP1 IE, S-SFH SP2 IE and S-SFH SP3 IE. The transmission periodicities of S-SFH SP1 IE, S-SFH SP2 IE and S-SFH SP3 IE are signaled through the S-SFH SP3 IE.
TABLE 3SP schedulingTransmissionTransmissionTransmissionperiodicityperiodicityperiodicityperiodicityinformationof S-SFH SP1of S-SFH SP2of S-SFH SP3000040 ms80 ms160 ms000140 ms80 ms320 ms0010-1111: reserved
A method for controlling a mobile station (MS) to update S-SFH SP IE (secondary super frame header subpacket information element) information will hereinafter be described in detail.
The mobile station (MS) receives P-SFH IE to confirm the S-SFH change count field. The base station (BS) increases a value assigned to the S-SFH change count field by one whenever the S-SFH IE information is updated (changed).
If the value of the S-SFH change count field is different from a value assigned to the MS, the MS determines that the S-SFH SP IE has been updated (changed), and recognizes the S-SFH SP change bitmap of the P-SFH IE such that it can confirm which S-SFH SP has been updated (changed).
In addition, P-SFH IE confirms the S-SFH scheduling information field to recognize which S-SFH SP IE is transmitted through a current superframe. When transmitting the S-SFH SP IE to be updated (stored and updated) in the current SFH, the corresponding S-SFH SP IE is confirmed and updated (stored and updated). In addition, in the case where the S-SFH SP IE to be updated (stored and updated) is not transmitted through the current SFH, the S-SFH SP IE is received at the next period in which the S-SFH SP IE to be updated (stored and updated) is transmitted, such that the received SFH SP IE is updated (stored and updated).
According to the conventional art, the MS must decode the POSFH at every superframe, confirm the S-SFH change count, and confirm whether the S-SFH SP IEs are changed, resulting in an increase in power consumption of the MS.
Next, a sleep mode operation according to the conventional art will hereinafter be described with reference to FIG. 1. While a mobile station (MS) communicates with a base station (BS) in a normal mode or an active mode, if there is no more traffic to be transmitted/received to/from the BS, the MS transmits a sleep request (hereinafter referred to as AAI_SLP-REQ) message requesting that the BS transition to a sleep mode. In response to the AAI_SLP-REQ message, the BS transmits a sleep response (hereinafter referred to as AAI_SLP-RSP) message to the MS. The MS having received the AAI_SLP-RSP message transitions to sleep mode using sleep parameters (such as a sleep cycle, a listening window, etc.) contained in the AAI_SLP-RSP message. In addition, the BS transmits an unsolicited AAI_SLP-RSP message to the MS such that the MS may transition to sleep mode.
FIG. 1 is a conceptual diagram illustrating a sleep mode operation of the MS according to the conventional art. Referring to FIG. 1, after the MS transitions from normal mode to sleep mode, an initial sleep cycle is applied to the MS such that the MS operates in the sleep mode. Upon completion of the transition to the sleep mode, a first sleep cycle includes only a sleep window.
From a second sleep cycle located after a first sleep cycle, the MS operates in the sleep mode using the sleep cycle including both the listening window and the sleep window. If the MS receives a traffic indication (TRF-IND) message including a negative indication message during the listening window, the MS detects the absence of downlink (DL) transmission traffic, and doubles a current sleep cycle. After the doubled sleep cycle ends, if the MS receives a TRF-IND message including a positive indication message during a listening window of the next sleep cycle, the MS resets a current sleep cycle to an initial sleep cycle.
The MS in the sleep mode has to include the latest system information transmitted through the SFH such that it can freely communicate with the BS using the latest system information. However, if a frame for P-SFH transmission is present in a sleep window of the MS, the MS is unable to receive the P-SFH.
In accordance with the above-mentioned conventional art, the MS needs to decode P-SFH at every superframe so as to determine whether S-SFH SP IEs are changed, resulting in an increase in MS power consumption. In addition, in the case of the MS operating in the sleep mode, if a frame for S-SFH transmission is present in the MS sleep window, the MS is unable to receive the P-SFH.